Secure data encoding for low-resource remote systems

ABSTRACT

A method includes receiving an input artefact and a set of shared parameters comprising a coding frame, one or more positioned elements, a travel path, and an initial position, and receiving an input artefact. The method includes initializing an output string and a head index and a tail index. The method includes traversing the travel path by, for each position: (i) determining whether the next position includes any positioned element; (ii) responsive to the next position not including any positioned element, filling the head index with a content character from the next position and incrementing the head index; (iii) responsive to next position including any positioned element, filling the tail index with a content character from the next position, and decrementing the tail index. The method includes setting said next position based on an attack position for the positioned element according to a variant of chess.

BACKGROUND

The present invention relates generally to the field of secure datatransmission, and more particularly to data encoding for use inlow-resource embedded systems such as Internet-of-Things (“IoT”)devices.

IoT introduces a wide range of embedded devices that have varying levelsof computing and power resources. Conventional strong cryptographymethods are often resource intensive and may provide an unnecessarydegree security for many IoT applications. Low-resource encodings thatrequire minimal additional memory and processing power can provide ameasure of security where strong cryptography is impractical.

SUMMARY

In one aspect, a computer-implemented method includes identifying aninput string and a set of shared parameters. The input string includesone or more ordered characters. The set of shared parameters includes(i) a coding frame including a plurality of spatially related positionswith each of the plurality of spatially related positions being fillableby any of the one or more ordered characters; (ii) one or morepositioned elements, each having defined therefor a location positionand one or more attack positions, the location position and each of theone or more attack positions being of the plurality of spatially relatedpositions, and the one or more attack positions being in a specifiedorder; (iii) a travel path including an order for traversing theplurality of spatially related positions; and (iv) an initial position,which is that of the plurality of spatially related positions that isfirst in the travel path. The computer-implemented method furtherincludes initializing a head index to a first character of the one ormore ordered characters, initializing a tail index to a last characterof the one or more ordered characters, and traversing the travel path toyield an output artefact by, for each next position of the plurality ofspatially related positions, beginning with the initial position: (i)determining whether the next position includes the location position forany active element of the one or more positioned elements; (ii)responsive to no active element having the location position at the nextposition: (a) filling the next position in the output artefact with thatof the one or more ordered characters that is identified by the headindex; (b) incrementing the head index forward by one character of theone or more ordered characters; (c) responsive to the head index beingequal to the tail index, terminating; and (d) advancing the nextposition according to the travel path; and (iii) responsive to theactive element having the location position at the next position: (a)filling the next position in the output artefact with that of the one ormore ordered characters that is identified by the tail index; (b)decrementing the tail index backward by one character of the one or moreordered characters; (c) responsive to the head index being equal to thetail index, terminating; (d) determining, for the active element, anactive attack position by selecting from the one or more attackpositions, based on the specified order and on whether each of the oneor more attack positions is valid; (e) responsive to the active attackposition existing for the active element, setting the next position tothe active attack position; and (f) responsive to no active attackposition existing for the active element, advancing the next positionaccording to the travel path. The result of the computer-implementedmethod is that the output artefact includes an encoding of the inputstring.

A corresponding computer-implemented method may be applied to decode theoutput artefact back into the input string. Corresponding computerprogram products and computer systems are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an operating environment, inaccordance with at least one embodiment of the present invention.

FIG. 2 is a block diagram depicting various data elements operated uponby a low-resource encoding program, in accordance with at least oneembodiment of the present invention.

FIG. 3 is a block diagram depicting various data elements operated uponby a decoding program, in accordance with at least one embodiment of thepresent invention.

FIG. 4A depicts a representation of a chess board coding frame with atravel path, in accordance with at least one embodiment of the presentinvention.

FIG. 4B depicts a representation of a chess board coding frame withpositioned elements represented as chess pieces, in accordance with atleast one embodiment of the present invention.

FIG. 5 is a flowchart diagram for a low-resource encoding program, inaccordance with at least one embodiment of the present invention.

FIG. 6 is a flowchart diagram for a decoding program, in accordance withat least one embodiment of the present invention.

FIG. 7 is a block diagram depicting various logical elements for acomputer system capable of executing program instructions, in accordancewith at least one embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a block diagram illustrating an operating environment,generally designated low-resource computing environment 100, inaccordance with at least one embodiment of the present invention. In thelow-resource computing environment 100 and IoT Device 102 may provide alow-resource computing environment 100. The low resource computingenvironment 100 may communicate with a recipient computing environment106 via an encoded channel 104. Both the low-resource computingenvironment 100 and the recipient computing environment 106 may begeneral purpose computers, such as that depicted in FIG. 7. Thelow-resource computing environment 100 may host a low-resource encodingprogram 101, and the recipient computing environment may host a decodingprogram 107.

In various embodiments, the IoT device 102 is an embedded device thatoperates within a distributed environment to form or communicate with acomputing service. The recipient computing environment 106 may be aphysical or virtual server, another IoT device, or any other physical,virtual, or logical system to which the IoT device would send an encodedmessage. Similarly, in various embodiments, the low-resource encodingprogram 101 may operate on a source computing environment (notnecessarily subject to resource restrictions) that would send encodedmessages to an IoT device in the role of the recipient computingenvironment 106 (which may be subject to low resource restrictions.

Often, whether sending or receiving applications running on IoT devicesonly need a low level of encoding. For instance, field sensors andactuators transmit and receive data that is not highly sensitive, butstill should not be transmitted in the clear. Specifically, an attackermay be able to listen to a signal in the clear from a field sensor andconstruct systems that react in unexpected ways or inject false datainto the signal. Such devices may benefit from a system which presents agood trade-off between a measure of data security on the one hand andreduced power consumption, memory usage, and processor time on theother.

Accordingly, in various embodiments, the encoded channel 104 may be adirect or indirect, wireless or wired link between the IoT device 102and the recipient computing environment 106. The encoded channel 104 maybe layered on top of a communications protocol, such as TCP/IP andcarried over a private or public data network including the Internet,mobile data networks, local Wi-Fi networks, etc.

Encoding according to various embodiments of the present invention mayproceed with reference to a chess board, such as the example depicted inFIGS. 4A and 4B. More specifically, however, FIG. 2 displays a blockdiagram of various logical data elements operated upon by thelow-resource encoding program 101. Similarly, FIG. 3 displays a blockdiagram of various logical data elements operated upon by the decodingprogram 107.

Referring now to FIG. 2, the low-resource encoding program may encode aninput string 200. The input string 200 may include one or more orderedcharacters 204. The ordered characters may belong to any set of human ormachine language characters, including binary, decimal, or hexadecimaldigits, as well as human-readable text in any language represented usingany standard or non-standard text encoding. Examples of possiblestandard text encodings include ASCII, UTF-8, UTF-16, UTF-32, Big5,Guobiao, ISO 8859, JIS X, etc. For the input string 200, thelow-resource encoding program 101 may define a head index 202 and a tailindex 206, which may be initialized to the beginning and end of theinput string 200, respectively. In alternative embodiments, more orfewer indices may be applied to the input string 200, and the startingpositions of such indices may be other than the beginning and end of theinput string 200.

Referring now to FIG. 3, the decoding program 107 may decode an outputstring 300 to retrieve the input string 200. The output string 300 mayinclude a plurality of ordered empty slots 304 into which characters ofthe same character set of the input string 200 may be placed by thedecoding program 107. The plurality of ordered empty slots 304 may beequal in number to the output string length 336. For the output string300, the decoding program 107 may define a head index 302 and a tailindex 306, which may be initialized to the beginning and end of theoutput string 300, respectively. In alternative embodiments, more orfewer indices may be applied to the output string 300, and the startingpositions of such indices may be other than the beginning and end of theoutput string 300. In various embodiments, the decoding program 107 mayoperate using the output string length 336, which may be predeterminedor transmitted to the recipient computing environment 106.

Referring now to FIG. 2, the low-resource encoding program 101 mayoperate using a set of shared parameters 210. The shared parameters 210may include a coding frame 212, which is includes a plurality ofspatially related positions 214. In general, the coding frame 212 may beof any shape in any number of logically defined spatial dimensions, withthe spatially related positions 214 being defined within the codingframe 212 as having a location with respect to other positions 214 orwith respect to an absolute measure, such as a coordinate system. Forexample, the coding frame 212 may include a chess board 400 as in FIGS.4A and 4B. In such embodiments, the coding frame 212 may include aplanar grid eight positions by eight positions in size, for sixty-fourtotal positions, as in chess. Alternative embodiments include: planargrids of different sizes, including non-square and non-rectangulargrids; frames having other than four neighbors per location, such as sixneighbors per location (hexagons) and three neighbors per location(equilateral triangles); and frames in more than two dimensions, such asa three dimensional eight position by eight position by eight positionchess board with five hundred twelve positions.

Referring still to FIG. 2, each of the plurality of spatially relatedpositions 214 may be fillable by any of the one or more orderedcharacters 204. That is, the low-resource encoding program 101 may copy,move, transmit, and insert, etc. characters 204 from the input string200 into positions 214 of the coding frame 212. The low-resourceencoding program may create an output artefact 230, which may be anobject, multidimensional array, list, or other data structure thatrepresents a filled instance of the coding frame 212, i.e., a codingframe instance 232. The coding frame instance 232 may be understood toinclude one or more fillable positions 234, which correspond to thepositions 214 and, when filled, carry the encoded data. The outputartefact 230 may be understood as including an encoding of the inputstring 200. Thus, the low-resource encoding program 101 may transmit theoutput artefact 230 to a recipient, such as the recipient computingenvironment 106. Transmission may occur over the encoded channel 104, asdescribed above.

The set of shared parameters 210 may further include a travel path 216.The travel path 216 may include an order for traversing the plurality ofspatially related positions 214. Any order of traversal is contemplatedfor various embodiments, including orders that do not include everyposition 214, include some positions 214 twice or multiple times, andorders that have cycles, branches, or other structures. An initialposition 218 may be identified as that of the plurality of spatiallyrelated positions 214 that is first in the travel path 216. FIG. 4Aprovides an example of the travel path 216 in the context of the chessboard 400 as the coding frame 212. In FIG. 4A, the chess board travelpath 402 is represented as the squares running between the darkenedlines, as shown. The darkened lines restrict the chess travel path 402to a single cycle of all squares of the chess board 400, which could betraversed in or two directions. It should be understood that variousembodiments contemplate the travel path as the spatially relatedpositions 214 as arranged in one dimension, however this does not changethe arrangement of the positions 214 within the coding frame 212 in anynumber of dimensions.

Referring still to the example of FIG. 4A, a starting square 404 (inthis example, A1) may be the initial position 218. An initial direction405 may further specify the direction of traverse for the chess travelpath 402. Thus, the travel path 216 is fully specified with the chessboard 400.

Referring now to FIG. 2, the set of shared parameters 210 may furtherinclude one or more positioned elements 220. Each of the one or morepositioned elements 220 may have defined therefor a location position222 and one or more attack positions 224. The location position 222 andone or more attack positions 224 may be positions of the plurality ofspatially related positions 214. The one or more attack positions 224for a particular positioned element may be defined in a specified order.The one or more positioned elements 220 and the one or more attackpositions 224 may defined in accordance with a variant of chess.

FIG. 4B depicts an example. In the depicted example, placed on the chessboard 400 is a plurality of chess pieces 410. Each chess piece 410 isdefined in accordance with standard chess, and accordingly is given acolor (i.e., white or black) and a name (i.e., pawn, knight, bishop,rook, king, or queen). Each chess piece 410 is defined to be at a givenposition (location position 222) as part of the set of shared parameters210. In the depicted embodiment of the invention, the chess pieces 410(i.e., positioned elements 220) have defined attack positions 224.

For example, the white queen 412 at F5 has certain moves available to itin standard chess, if white's move. Specifically, the white queen 412may move: (i) up file F at most one square to F6 414D, where it can gono further because it can neither collocate with nor pass through thewhite pawn at F7; (ii) diagonally up and right at most two squares to H7414D, where it can go no further because it has reached the edge of thechess board 400; (iii) right along rank 5 at most two squares to H5414E, where it can go no further because it has reached the edge of thechess board 400; (iv) diagonally down and right up to two squares to H3,where it would capture the black pawn 413A and must stop; (v) down alongrank F at most three squares to F2, where it would capture the blackpawn 413B and must stop; (vi) diagonally down and left up to foursquares to B1 414A, where it can go no further because it has reachedthe edge of the chess board 400; (vii) left along rank 5 at most onesquare to E5, where it would capture the black knight 413C and muststop; and (viii) diagonally up and left at most three squares to C8414G, where it can go no further because it has reached the edge of theboard. Of these possible attack positions, the set of shared parameters210 may include an ordered preference for attacks, if valid. Forexample, the white queen 412 may have defined the preference: attackdown the file as far as possible; if there is no valid attack down thefile, attack diagonally down and left as far as possible; if there is novalid attack down and left, attack right along the rank exactly threesquares; if it is not valid to attack right along the rank exactly threesquares, attack diagonally up and left one square; etc.

In some embodiments, the low-resource encoding program 101 may derivethe potential attack positions based on the names and colors of thepositioned elements 220 and the rules of chess or a variant of chess (inthe claims, “a variant of chess” includes standard chess). In suchembodiments, the names and colors of the pieces 410 (i.e., black pawn,white rook) may be specified, and it is possible to determine where thepieces may attack. In alternative embodiments, it is not necessary tospecify the names and colors of the positioned elements 220, but onlytheir arbitrarily defined valid attack positions 224 and preferenceorder among the attack positions 224. It should be noted that variousembodiments of the invention do not represent actual movement of thepositioned elements 220, but rather rely on where the positionedelements 220 may validly move and/or attack, as described below.

Referring now to FIG. 3, the decoding program 107 operates on dataelements broadly similarly to those of the low-resource encoding program101. The decoding program 107 receives the input artefact 330, whichincludes the coding frame instance 332, which has filled positions 334,suitable for decoding. Each filled position 334 is fillable by a contentcharacter selected from the set of characters. In addition, embodimentsof the decoding program 107 may operate on the specified output length336, which corresponds to the length of the decoded output string 300.The output length 336 may be set in advance as a property of the systemin which the decoding program 107 operates, or the output length 336 maybe transmitted with the input artefact 330 as additional input.

Similarly with the shared parameters 210 of the low-resource encodingprogram 101, the decoding program 107 operates on shared parameters 310.The shared parameters 310 include a coding frame 312, includingspatially related positions 314, defined similarly to the coding frame212 and spatially related positions 214. Distinctly, the spatiallyrelated positions 314 generally come pre-filled with characters 315 uponwhich the decoding program 107 operates. A travel path 316 and aninitial position 318 are defined for the spatially related positions 314in a manner similar to the travel path 216 and initial position 218. Theshared parameters 310 for the decoding program 107 may further includeone or more positioned elements 320, each having defined therefor alocation position 322 and one or more attack positions 324 in aspecified preferential order, similarly to the corresponding sharedparameters 210.

Referring now to FIG. 5, FIG. 5 is a flowchart diagram for alow-resource decoding program 101, in accordance with at least oneembodiment of the invention. At step 500, the low-resource encodingprogram identifies the input string 200 and the set of shared parameters210. At step 505, the low-resource encoding program 101 may initializethe head index 202 to the first character of the one or more orderedcharacters 204, and the low-resource encoding program 101 may furtherinitialize the tail index 206 to the last character of the one or moreordered characters 204.

Referring still to the flowchart diagram of FIG. 5, at decision block510, the low-resource encoding program 101 traverses the travel path 216to yield the output artefact 230 by processing the other steps in aloop, for each next position of the plurality of spatially relatedpositions 214, and beginning with the initial position 218. The nextposition may be understood as that of the spatially related positions214 that the low-resource encoding program 101 is processing in thecurrent iteration. The processing loop of decision block 510 may beunderstood as starting with the initial position 218 in the travel path216, but it is not assumed that the entire travel path 216 will betraversed in order, that all positions 214 will be visited, or that, insome embodiments, any given position 214 will not be traversed multipletimes. Specifically, the actual order of traversing the positions 214depends not only on the travel path 216, but also on the attackpositions 224, as described below.

The output artefact 230 may be instantiated, created, or generated,pursuant to decision block 510, or in advance. The output artefact 230may be understood to include the coding frame instance 232 with fillablepositions 234. The low-resource encoding program may fill the fillablepositions 234 as it iterates over decision block 510, with the codingframe instance 232 being taken as complete upon the low-resourceencoding program 101 terminating, as described below.

The low-resource encoding program proceeds, for the next position, atdecision block 515 by determining whether the next position includes thelocation position 222 for any active element of the one or morepositioned elements 220. The active element may be understood as that ofthe positioned elements 220 (i.e., chess pieces 410) that is present inthe next position. In some embodiments, the positioned elements 220 maybe restricted so that only one positioned element 220 (the activeelement) may be present in a given position 214 (the next position);this restriction is equivalent to standard chess, wherein only one piecemay occupy a square at a time. In other embodiments, however, thisrestriction need not necessarily apply, and the invention may bepracticed so as to take account of multiple positioned elements 220present in the same position 214.

Responsive to no active element having its location position 222 at thenext position (decision block 515, NO branch), the low-resource encodingprogram 101 proceeds at step 520 by filling the next position in theoutput artefact 230 (i.e., that of the fillable positions 234 thatcorresponds to the next position) with that of the one or more orderedcharacters 204 that is identified by the head index 202. In FIG. 5, theoutput artefact 599 is represented as receiving the filling data fromstep 520. The low-resource encoding program 101 may proceed at step 525by incrementing the head index 202 forward by one character of the oneor more ordered characters 204.

At decision block 530, the low-resource encoding program 101 comparesthe head index 202 with the tail index 206. Responsive to the head index202 being equal to the tail index 206, the low-resource encoding program101 terminates (decision block 530, YES branch). If the head index 202is equal to the tail index 206, then it may be understood that theentire input string 200 has been encoded into the output artefact 230,and the output artefact 230 may be understood to include an encoding ofthe input string 200. More broadly, the head index 202 equalling thetail index 206 may be taken as all characters 204 having been processed,by any means of iteration or simultaneous consideration. At step 535(decision block 530, left NO branch, having come from the left at step525), the low-resource encoding program 101 may advance the nextposition according to the travel path 216 and returning to process thenew next position at decision block 510.

Referring now to decision block 515, the low-resource encoding program101 may determine whether the next position includes the locationposition 222 for any active element of the one or more positionedelements 220. Responsive to the active element having its locationposition 222 at the next position (decision block 515, YES branch) thelow-resource encoding program 101 proceeds at step 540 by filling thenext position in the output artefact 230 (i.e., that of the fillablepositions 234 that corresponds to the next position) with that of theone or more ordered characters 204 that is identified by the tail index206. Thus, in at least some embodiments, by pulling characters from theinput string 200 out of order (from the front or the back, depending onthe chess pieces 410), rather than by directly substituting characters204 for other characters, the low-resource encoding program 101 achievesa cipher that is both reasonably robust and does not require theprocessor-intensive arithmetic needed for cryptography. Referring backto FIG. 5, the output artefact 599 is represented as receiving thefilling data from step 540. The low-resource encoding program 101 mayproceed at step 545 by decrementing the tail index 206 backward by onecharacter of the one or more ordered characters 204.

Referring still to the flowchart diagram of FIG. 5, at decision block530, the low-resource encoding program 101 compares the head index 202with the tail index 206. Responsive to the head index 202 being equal tothe tail index 206, the low-resource encoding program 101 terminates(decision block 530, YES branch). As above, the head index 202 equallingthe tail index 206 may be understood to mean that the encoding algorithmhas completed. At decision block 550 (decision block 530, right NObranch, having come from the right at step 545), the low-resourceencoding program 101 may determine, for the active element, an activeattack position by selecting from the one or more attack positions 224,based on the specified order of the attack positions 224 and on whethereach of the one or more attack positions 224 is valid. The active attackposition refers to that of the attack positions 224 that thelow-resource encoding program selects. The selection step may beachieved by iterating over or traversing the attack positions 224 inorder of preference, until a valid attack position 224 is found.

In some embodiments, valid attack positions are restricted to thosepositions 214 that have not already been filled in the coding frameinstance 232. Additionally, validity, in the context of attack positions224 may include that the attack position is allowed, according topredetermined rules (e.g., of chess, of some other game, or of arbitraryconstruction). These predetermined rules, unlike the predeterminedattack positions 224 themselves, generally take into account thepositions and properties of other positioned elements 220, while theattack positions 224 define the properties of the positioned element inrelation to the space in which it is positioned (i.e., the coding frame212). In some embodiments, the predetermined rules may be the rules of avariant of chess, including standard chess. Thus, according to the rulesof standard chess, examples of invalid moves include: (i) chess pieces410 attacking off the board 400; (ii) chess pieces 410 attacking into asquare occupied by a piece of the same color; (iii) chess pieces otherthan knights attacking through other pieces; and (iv) chess pieces 410attacking such that the king of the same color is placed in check.

Referring still to the flowchart diagram of FIG. 5, responsive to theactive attack position existing for the active element (decision block550, YES branch; i.e., a valid attack was selected from the attackpositions 224), at step 555, the low-resource encoding program 101 setsthe next position to the active attack position, and the low-resourceencoding program 101 proceeds to decision block 510 to process thenow-shifted next position. For various embodiments, the shifting of thenext position in response to encountering the active element introducesan additional layer of reasonably robust encoding to the cipher that,like taking from the end of the input string 200, also does not requireprocessor-intensive arithmetic as is the case for cryptography.Referring now back to FIG. 5, responsive to no active attack positionexisting for the active element (decision block 550, NO branch), thelow-resource encoding program 101 may, at step 535, advance the nextposition according to the travel path 216 and proceed with processingthe next position at decision block 510.

Referring now to FIG. 6, FIG. 6 displays a flowchart diagram for thedecoding program 107, in accordance with at least one embodiment of thepresent invention. Except where differences are discussed in detail, thedecoding program 107 may be understood to proceed similarly to thelow-resource encoding program 101. At step 600, the decoding program 107receives the shared parameters 310. Also at step 600, the decodingprogram 107 receives the input artefact 330. At step 602, the decodingprogram 107 identifies the output string length 336. As stated above,the output string length may be received or predetermined. At step 604,the decoding program initializes the output string 300. At step 605, thedecoding program 107 may initialize the head index 302 to the first slotof the plurality of slots 304, and the decoding program 107 may furtherinitialize the tail index 306 to the last slot of the plurality of slots304.

At decision block 610, the decoding program 107 traverses the travelpath 316 to for the input artefact 330 by processing the other steps ina loop, for each next position of the plurality of spatially relatedpositions 314, and beginning with the initial position 318. The decodingprogram 107 proceeds, for the next position, at decision block 615 bydetermining whether the next position includes the location position 322for any active element of the one or more positioned elements 320.Responsive to no active element having its location position 322 at thenext position (decision block 615, NO branch), the decoding program 107proceeds at step 620 by filling that slot of the plurality of orderedempty slots 304 that is identified by the head index 302 with thecontent character from the next position. In FIG. 6, the output string699 is represented as receiving the filling data from step 620. Thedecoding program 107 may proceed at step 625 by incrementing the headindex 302 forward by one slot of the one or more ordered slots 304.

At decision block 630, the decoding program 107 compares the head index302 with the tail index 306. Responsive to the head index 302 beingequal to the tail index 306, the decoding program 107 terminates(decision block 630, YES branch). If the head index 302 is equal to thetail index 306, then it may be understood that the entire input artefact330 has been decoded into the output string 300, and the output string300 may be understood to include a decoding of the input artefact 330.More broadly, the head index 302 equalling the tail index 306 may betaken as all slots 304 having been processed, by any means of iterationor simultaneous consideration. At step 635 (decision block 630, left NObranch, having come from the left at step 625), the decoding program 107may advance the next position according to the travel path 316 andreturning to process the new next position at decision block 610.

Referring now to decision block 615, the decoding program 107 maydetermine whether the next position includes the location position 322for any active element of the one or more positioned elements 320.Responsive to the active element having its location position 222 at thenext position (decision block 615, YES branch) the decoding program 107proceeds at step 640 by filling that slot of the plurality of orderedempty slots 304 that is identified by the tail index 306 with thecontent character from the next position. The output string 699 isrepresented as receiving the filling data from step 640. The decodingprogram 107 may proceed at step 645 by decrementing the tail index 306backward by one slot of the plurality of ordered slots 304.

Referring still to the flowchart diagram of FIG. 6, at decision block630, the decoding program 107 compares the head index 302 with the tailindex 306. Responsive to the head index 302 being equal to the tailindex 306, the decoding program 107 terminates (decision block 630, YESbranch). As above, the head index 302 equalling the tail index 306 maybe understood to mean that the decoding algorithm has completed. Atdecision block 650 (decision block 630, right NO branch, having comefrom the right at step 645), the decoding program 107 may determine, forthe active element, an active attack position by selecting from the oneor more attack positions 324, based on the specified order of the attackpositions 324 and on whether each of the one or more attack positions324 is valid. The active attack position refers to that of the attackpositions 324 that the decoding program selects. The selection step maybe achieved by iterating over or traversing the attack positions 324 inorder of preference, until a valid attack position 324 is found. In someembodiments, valid attack positions 224 for the decoding program 107 arerestricted to those positions 314 that not have not already beenprocessed from the coding frame instance 332 into the output string 300.This is equivalent to, in the context of the low-resource encodingprogram 101, excluding positions 214 that have already been filled. Inaddition, validity may depend upon predetermined rules in the mannerdescribed above for the low-resource encoding program 101.

Referring still to the flowchart diagram of FIG. 6, responsive to theactive attack position existing for the active element (decision block650, YES branch; i.e., a valid attack was selected from the attackpositions 324), the decoding program 107 sets the next position to theactive attack position, and the decoding program 107 proceeds todecision block 610 to process the now-shifted next position. Referringnow back to decision block 650, responsive to no active attack positionexisting for the active element (decision block 650, NO branch), thedecoding program 107 may, at step 635, advance the next positionaccording to the travel path 316 and proceed with processing the nextposition at decision block 610.

In various embodiments of the low-resource encoding program 101, theshared parameters 210 may be configured to change based on thepositioned elements 220. Specifically, the low-resource encoding program101 and decoding program 107 may evolve at least one of the one or moreattack positions 224 and the specified order for the attack positions224, based on at least one of the next positions and that of the one ormore ordered characters that is identified by the tail index 206. Thus,the low-resource encoding program causes shifts in or evolves the sharedparameters in response to an active element being present at the nextposition, but chooses how to evolve the shared parameters based on thecontent. The decoding program 107 may evolve the shared parameters 310correspondingly to retrieve the encoded data. In such embodiments, thelow-resource encoding program 101 may effectively increase the expectedunpredictability of the encoded data without processor-intensivearithmetic, and in a way that incorporates both the shared parametersthemselves (the positioned elements 220) and the input string 200. Infurther embodiments, the shared parameters 310 may evolve based on anyof the shared parameters 210, the head index 202, other properties ofthe input string 200, etc.

In various embodiments, the low-resource encoding program may append anadditional data to the input string 200. Correspondingly, the decodingprogram 107 may decode the additional data from the input artefact 330.At a minimum, the additional data further obfuscates the original dataand increases the robustness of the encoding at low cost. To this end,the additional data may include random data. In other embodiments, thelow-resource encoding program 101 may generate a checksum for the inputstring 200 without the additional data and append the checksum as theadditional data. The decoding program 107 may then check its results forerrors using the checksum. In other embodiments, the low-resourceencoding program 101 may include a code word as the additional data andevolve the set of shared parameters, based on the code word. Forexample, the low-resource encoding program may append the code word“first” to a given input string 200, and then for the next input string200 reflect the positioned elements 320 about the coding frame 312 ormove the initial position 318. The decoding program 107, responsive todecoding the code word “first”, may make corresponding changes to theshared parameters 310 for the next input artefact 330. Any of the sharedparameters 210 may be evolved in this manner over multiple iterations ofthe methods described, thus increasing the robustness of the encoding.

FIG. 7 is a block diagram depicting components of a computer 700suitable for executing the low-resource encoding program 101 and/or thedecoding program 107. FIG. 7 displays the computer 700, the one or moreprocessor(s) 704 (including one or more computer processors), thecommunications fabric 702, the memory 706, the RAM, the cache 716, thepersistent storage 708, the communications unit 710, the I/O interfaces712, the display 720, and the external devices 718. It should beappreciated that FIG. 7 provides only an illustration of one embodimentand does not imply any limitations with regard to the environments inwhich different embodiments may be implemented. Many modifications tothe depicted environment may be made.

As depicted, the computer 700 operates over a communications fabric 702,which provides communications between the cache 716, the computerprocessor(s) 704, the memory 706, the persistent storage 708, thecommunications unit 710, and the input/output (I/O) interface(s) 712.The communications fabric 702 may be implemented with any architecturesuitable for passing data and/or control information between theprocessors 704 (e.g., microprocessors, communications processors, andnetwork processors, etc.), the memory 706, the external devices 718, andany other hardware components within a system. For example, thecommunications fabric 702 may be implemented with one or more buses or acrossbar switch.

The memory 706 and persistent storage 708 are computer readable storagemedia. In the depicted embodiment, the memory 706 includes a randomaccess memory (RAM). In general, the memory 706 may include any suitablevolatile or non-volatile implementations of one or more computerreadable storage media. The cache 716 is a fast memory that enhances theperformance of computer processor(s) 704 by holding recently accesseddata, and data near accessed data, from memory 706.

Program instructions for the low-resource encoding program 101 and/orthe decoding program 107 may be stored in the persistent storage 708 orin memory 706, or more generally, any computer readable storage media,for execution by one or more of the respective computer processors 704via the cache 716. The persistent storage 708 may include a magnetichard disk drive. Alternatively, or in addition to a magnetic hard diskdrive, the persistent storage 708 may include, a solid state hard diskdrive, a semiconductor storage device, read-only memory (ROM),electronically erasable programmable read-only memory (EEPROM), flashmemory, or any other computer readable storage media that is capable ofstoring program instructions or digital information.

The media used by the persistent storage 708 may also be removable. Forexample, a removable hard drive may be used for persistent storage 708.Other examples include optical and magnetic disks, thumb drives, andsmart cards that are inserted into a drive for transfer onto anothercomputer readable storage medium that is also part of the persistentstorage 708.

The communications unit 710, in these examples, provides forcommunications with other data processing systems or devices. In theseexamples, the communications unit 710 may include one or more networkinterface cards. The communications unit 710 may provide communicationsthrough the use of either or both physical and wireless communicationslinks. The low-resource encoding program 101 and/or the decoding program107 may be downloaded to the persistent storage 708 through thecommunications unit 710. In the context of some embodiments of thepresent invention, the source of the various input data may bephysically remote to the computer 700 such that the input data may bereceived and the output similarly transmitted via the communicationsunit 710.

The I/O interface(s) 712 allows for input and output of data with otherdevices that may operate in conjunction with the computer 700. Forexample, the I/O interface 712 may provide a connection to the externaldevices 718, which may include a keyboard, keypad, a touch screen,and/or some other suitable input devices. External devices 718 may alsoinclude portable computer readable storage media, for example, thumbdrives, portable optical or magnetic disks, and memory cards. Softwareand data used to practice embodiments of the present invention may bestored on such portable computer readable storage media and may beloaded onto the persistent storage 708 via the I/O interface(s) 712. TheI/O interface(s) 712 may similarly connect to a display 720. The display720 provides a mechanism to display data to a user and may be, forexample, a computer monitor.

The programs described herein are identified based upon the applicationfor which they are implemented in a specific embodiment of theinvention. However, it should be appreciated that any particular programnomenclature herein is used merely for convenience, and thus theinvention should not be limited to use solely in any specificapplication identified and/or implied by such nomenclature.

The present invention may be a system, a method, and/or a computerprogram product at any possible technical detail level of integration.The computer program product may include a computer readable storagemedium (or media) having computer readable program instructions thereonfor causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, configuration data for integrated circuitry, oreither source code or object code written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Smalltalk, C++, or the like, and procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The computer readable program instructions may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider). In some embodiments, electronic circuitry including,for example, programmable logic circuitry, field-programmable gatearrays (FPGA), or programmable logic arrays (PLA) may execute thecomputer readable program instructions by utilizing state information ofthe computer readable program instructions to personalize the electroniccircuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in the Figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

What is claimed is:
 1. A computer program product comprising one or morecomputer readable storage media and program instructions stored on saidone or more computer readable storage media, said program instructionscomprising instructions to: receive a set of shared parameters, said setof shared parameters comprising: a coding frame, said coding framecomprising a plurality of spatially related positions; each of saidplurality of spatially related positions being fillable by a contentcharacter selected from of a set of characters; one or more positionedelements, each of said one or more positioned elements having definedtherefor a location position and one or more attack positions, saidlocation position and each of said one or more attack positions being ofsaid plurality of spatially related positions, said one or more attackpositions being in a specified order; a travel path, said travel pathcomprising an order for traversing said plurality of spatially relatedpositions; and an initial position, said initial position being that ofsaid plurality of spatially related positions that is first in saidtravel path; receive an input artefact, said input artefact comprisingan instance of said coding frame wherein at least one of said pluralityof spatially related positions is filled by said content character;identify an output string length; initialize an output string, saidoutput string comprising a plurality of ordered empty slots, saidplurality of ordered empty slots being equal in number to said outputstring length; initialize a head index to a first slot of said pluralityof ordered empty slots; initialize a tail index to a last slot of saidplurality of ordered empty slots; for said input artefact, traverse saidtravel path by, for each next position of said plurality of spatiallyrelated positions, beginning with said initial position: determiningwhether said next position comprises said location position for anyactive element of said one or more positioned elements; responsive to noactive element having said location position at said next position:filling that slot of said plurality of ordered empty slots that isidentified by said head index with said content character from said nextposition; incrementing said head index forward by one slot of saidplurality of ordered empty slots; responsive to said head index beingequal to said tail index, terminating; and advancing said next positionaccording to said travel path; responsive to said active element havingsaid location position at said next position: filling that slot of saidplurality of ordered empty slots that is identified by said tail indexwith said content character from said next position; decrementing saidtail index backward by one slot of said plurality of ordered emptyslots; responsive to said head index being equal to said tail index,terminating; determining, for said active element, an active attackposition by selecting from said one or more attack positions, based onsaid specified order and on whether each of said one or more attackpositions is valid; responsive to said active attack position existingfor said active element, setting said next position to said activeattack position; and responsive to no active attack position existingfor said active element, advancing said next position according to saidtravel path; whereby said output string comprises a decoding of saidinput artefact; wherein said coding frame comprises a planar grid, saidgrid being eight positions by eight positions in size; wherein said oneor more positioned elements and said one or more attack positions aredefined in accordance with a variant of chess; wherein said instructionsto traverse said travel path further comprise instructions to evolve atleast one of said one or more attack positions and said specified order,based on at least one of said next position and that of said one or moreordered characters that is identified by said tail index; wherein saidprogram instructions further comprise instructions to decode anadditional data from said input artefact, said additional datacomprising a code word, and evolving said set of shared parameters basedon said code word; and wherein said program instructions are performedin a low-resource computing environment.